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AvailabilityVersions fork

Overview

This is a community-maintained fork of Apple's AvailabilityVersions repo, which provides version number definitions and availability macros for Apple platforms.

For more information the branching scheme, please see docs/PatchBranchingScheme.md.

Background

Apple's official AvailabilityVersions distribution (last updated as version 155) has not had its availability.dsl file updated since iOS 17.3. This causes the open-source dyld to fail identifying newer OS versions, as the <dyld/VersionMap.h> and sVersionMap data structures remain outdated.

This fork reconstructs the missing availability data from dyld's internal version mappings to maintain compatibility with current and future OS releases.

Reconstruction Process

Since Apple no longer updates the DSL file, we reconstruct availability.dsl entries by extracting version data from dyld binaries found in OS releases.

Step 1: Extract Version Set Data from dyld Binary

Use a disassembler (e.g., Hopper, IDA Pro, Binary Ninja) or otool to locate the sVersionMap symbol in the dyld binary (/usr/lib/dyld):

The VersionSetEntry structures appear as arrays of hexadecimal values:

__ZN5dyld3L11sVersionMapE:  // dyld3::sVersionMap
struct VersionSetEntry {
    0x7e80600,    // .set
    0xf0600,      // .macos
    0x120600,     // .ios
    0xb0600,      // .watchos
    0x120600,     // .tvos
    0x90600,      // .bridgeos
    0x180600,     // .driverkit
    0x20600       // .visionos
}

Field Order (as defined in VersionMap.h):

  1. set - Version set identifier
  2. macos - macOS version
  3. ios - iOS version
  4. watchos - watchOS version
  5. tvos - tvOS version
  6. bridgeos - bridgeOS version
  7. driverkit - DriverKit version
  8. visionos - visionOS version

Step 2: Decode Version Numbers

Version numbers use the format 0x00MMMMRRRR where:

  • MMMM: Major.Minor version in hex
  • RRRR: Revision/patch version in hex

Examples:

  • 0x007e80600 decodes to 2024.6.0 (0x7e8 = 2024, 0x06 = 6, 0x00 = 0)
  • 0x00120600 decodes to 18.6.0 (0x12 = 18, 0x06 = 6, 0x00 = 0)
  • 0x000f0600 decodes to 15.6.0 (0x0f = 15, 0x06 = 6, 0x00 = 0)

Important: Set versions for 2024 releases use the simplified format 2024.N.0:

  • fall_2024: 2024.0.0 → 0x007e80000
  • 2024_SU_B: 2024.1.0 → 0x007e80100
  • 2024_SU_C: 2024.2.0 → 0x007e80200
  • 2024_SU_G: 2024.6.0 → 0x007e80600

Platform versions decode normally using their actual OS version numbers.

Step 3: Determine Darwin Kernel Version

The third parameter (uversion) in each set definition corresponds to the Darwin kernel version. Query from:

Example mappings:

  • macOS 15.0 / iOS 18.0 → Darwin 24.0.0
  • macOS 15.1 / iOS 18.1 → Darwin 24.1.0
  • macOS 15.6 / iOS 18.6 → Darwin 24.6.0

Step 4: Add DSL Entries

Follow the established naming convention for set names:

set         2024_SU_G           2024.6.0     24.6.0
version     macos               15.6
version     ios                 18.6
version     tvos                18.6
version     watchos             11.6
version     bridgeos            9.6
version     driverkit           24.6
version     visionos            2.6

Note: Set names follow previous conventions (e.g., fall_YYYY, YYYY_SU_X) and may differ from Apple's internal naming.

Example: Complete Extraction Workflow

Given this binary data from dyld:

0x7e80600, 0xf0600, 0x120600, 0xb0600, 0x120600, 0x90600, 0x180600, 0x20600

  1. Decode versions:

    • Set: 2024.6.0
    • macOS: 15.6.0
    • iOS: 18.6.0
    • watchOS: 11.6.0
    • tvOS: 18.6.0
    • bridgeOS: 9.6.0
    • DriverKit: 24.6.0
    • visionOS: 2.6.0

  2. Lookup Darwin version: 24.6.0 (from Apple Wiki or system)

  3. Create DSL entry:

set         2024_SU_G           2024.6.0     24.6.0
version     macos               15.6
version     ios                 18.6
version     tvos                18.6
version     watchos             11.6
version     bridgeos            9.6
version     driverkit           24.6
version     visionos            2.6

File Structure

  • availability.dsl - Domain-specific language defining platform versions and sets
  • availability - Python script for querying and preprocessing version data
  • templates/ - Header templates with preprocessing macros
  • Generated outputs:
    • <dyld/VersionMap.h> - Version set mapping table
    • <Availability.h> - Availability macros and version defines

Building

The build system uses CMake, with a Makefile wrapper for compatibility:

make install

Build process:

  1. Self-preprocess availability script to embed DSL content
  2. Preprocess all template files using the embedded DSL data
  3. Install processed files to DSTROOT

Usage

Query platform versions:

# List all iOS versions
/usr/local/libexec/availability --ios

# List all version sets (YAML format)
/usr/local/libexec/availability --sets

# Preprocess a template file
/usr/local/libexec/availability --preprocess input.h output.h

Contributing

When adding new OS versions:

  1. Extract version data from the latest dyld binary using a disassembler
  2. Decode hexadecimal versions to decimal format
  3. Verify Darwin kernel version from official sources
  4. Follow existing naming conventions for set names
  5. Maintain chronological order in availability.dsl
  6. Test generated headers for correctness

License

This project maintains compatibility with Apple's original licensing terms. See individual file headers for details.

See Also